Apktool's build path derives dex output paths from decoded-project directory names beginning with smali_ by replacing @ with the platform path separator and appending .dex. A malicious decoded project can use names such as smali_..@..@..@..@outside-owned so that apktool b --force --no-apk writes or overwrites a .dex file outside /build/apk.

Please confirm the smali_* directories are hardened and don't allow directory traversal.